Water-catalyzed iron-molybdenum carbyne formation in bimetallic acetylene transformation

Transition metal carbyne complexes are of fundamental importance in carbon-carbon bond formation, alkyne metathesis, and alkyne coupling reactions. Most reported iron carbyne complexes are stabilized by incorporating heteroatoms. Here we show the synthesis of bioinspired FeMo heterobimetallic carbyne complexes by the conversion of C₂H₂ through a diverse series of intermediates. Key reactions discovered include the reduction of a μ-η²:η²-C₂H₂ ligand with a hydride to produce a vinyl ligand (μ-η¹:η²-CH = CH₂), tautomerization of the vinyl ligand to a carbyne (μ-CCH₃), and protonation of either the vinyl or the carbyne compound to form a hydrido carbyne heterobimetallic complex. Mechanistic studies unveil the pivotal role of H₂O as a proton shuttle, facilitating the proton transfer that converts the vinyl group to a bridging carbyne.